The proposed work concerns three areas of investigation: 1. A relatively pure alpha cell preparation will be searched for with hopes of correlating biochemical parameters with glucagon secretion. 2. The influence of beta cells upon alpha cells within islets will be evaluated. There are indications that the local secretion of insulin exerts a suppressive effect upon glucagon secretion. 3. The mechanisms of alpha cell suppression by glucose will be studied. It is not known whether the glucose effects are exerted via a membrane action or by the consequences of glucose metabolism.